Ice Crystals - the variation in shading is a combination of the sky and
clouds reflected, and stones and water plants under the ice.

To give you an idea of what is going on here, these were shot at an alpine lake
that is about 85% frozen solid still, with just the edges open. Each night the
water in the edges freezes, and the shifting ice and currents in the lake
influence the formation of the ice crystals until all sorts of shapes form.
Mostly they look like feathers, and range in size from about 6 inches to
about 3 feet long - here are some I shot about 2 weeks ago
(also several others in that gallery) - http://www.pbase.com/cindyd/image/43248471
and here is the lake shot this morning so you can visualize this better:


The ice was popping a little this morning - sounded like a shotgun blast
and echoed off those cliffs. But this last fall when it was starting to form,
the ice cracking sounded like dynamite blasts it was so loud - and then it
would go to haunting sounds that somewhat resembled whale songs -
and then to something more like a Praire Chicken call, or a wounded dog yelping,
and other strange noises. It was a little unnerving. I visited a few times
this winter and walked across and took some panos from the middle.
Enjoy, Cindy